The 2021/2 Classification for Output Areas (2021/2 OAC) is a hierarchical geodemographic classification across the UK which identifies areas of the country with similar characteristics. It was developed by the ESRC Geographic Data Service (GeoDS) in partnership with the Office for National Statistics (ONS). The classification contains the following breakdown of Output Areas into 8 different supergroups, into which are nested 21 groups and 52 sub-groups.
Content
The data is available for download at the bottom of this page. Also available for download are a methodological paper, which outlines the approach taken to develop the classification, Local Authority atlases, and pen portraits, which provide additional information about the variables and terms used. Classification geodata can also be downloaded below.
Quality, Representation and Bias
A journal article (see link below) accompanies an earlier version 2021 OAC which provides a thorough evaluation. The classification was created using 2021 Census Output Area data for England and Wales; aggregate published 2021 Northern Ireland data, apportioned to 2011 small area census geography; and 2011 Scottish Census results carried forward in adjusted or unadjusted form. This version of the data was known as UK-OAC Modelled, and is available on specific request, via the article's corresponding author, for research reproducibility purposes.
In general terms, a geodemographic classification presents a best effort of the authors to represent the characteristics of the population and geographic context, however, there are decisions made during the classification process that guide these representations. Again for a full overview of these decisions and their rationale, see the published paper.
Version History
- 1.0 - OAC 2001
- 2.0 - OAC 2011
- 3.0 - OAC 2021 (November 2023) Released for England/Wales.
- 3.0.1 - Addition of index scores by local authority.
- 3.0.2 - Addition of group populations by local authority.
- 3.1 - UK-OAC Modelled (November 2023)
- 3.2 - UK-OAC (January 2025)
In version 3.2 the following Pen Portraits changed their name: 4b1 changed from Generational Migrants to Migrant Families. 8b3 changed from Young Families and Neighbourhood Turnover to Young Family Flat Renters. Many pen portrait descriptions were also updated.
In December 2025, Version 3.2 was made an Open dataset and renamed OAC 2021/2.
